Morphology-based data elimination from medical image data

Modern medical imaging lets us create accurate computer models of anatomical structures. Some of these models can be animated to visualize joint kinematics. A model's size and complexity can significantly affect the efficiency of any desired animation or interactive manipulation. The model normally takes the form of a polygonal mesh; the more facets in the mesh, the slower the rendering process. Beyond a certain limit, real time interaction becomes impractical because the frame rate (image regeneration) is too slow. The many methods proposed for reducing the number of polygons in computer models normally entail a loss of detail in the final model. In some applications, retaining detail may be important. Joint kinematics, which we were investigating, falls into this category, and we sought a way to reduce the input data volume without introducing a corresponding decrease in the isosurface resolution. Our application requires only the bone's external surface, which is found by segmenting radiological data obtained from computerized tomodensitometry (a CT scan). By analyzing local bone morphology, we were able to identify and eliminate nearly 50 percent of the polygons generated by standard segmentation techniques, while retaining the full resolution of the required isosurface. The article discusses the relationships between bone morphology and bone intensity in a medical imaging data set and describes how these relationships can help us reduce the polygon count in the surface models generated.